When displaying and showing items of jewelry that include gemstones, such as diamonds, it is desirable to provide a lighting environment that enables the visually perceptible features of the gemstones to be readily observed. For example, cut diamonds exhibit visually perceptible qualities generally referred to as “fire” and “scintillation”, that strongly influence an observer's subjective evaluation of the aesthetics of a diamond. The term “fire” usually refers to the rainbow colours that may be observed in a diamond as a result of the refraction of light entering and leaving the facets of the diamond, and the dispersion of the light within the diamond. The term “scintillation” usually relates to the “sparkle” of a diamond, and refers to flashes of light that may be visible within a diamond when either the diamond or the observer's viewing position moves relative to a source of light.
In order to best highlight features of a gemstone such as fire and scintillation, it is undesirable to substantially flood the environment with light. Rather, it is generally considered that point sources of lighting are the most effective, since each point source produces distinct reflections and other optical effects within a gemstone producing visible results that are clearly discernable by an observer. Accordingly, in modern jewelry stores and showrooms the most popular light sources are halogen lamps, mounted in fittings having rear reflectors. Since halogen lamps are relatively small, they provide a good approximation to a point light source having a concentrated and reasonably intense light output. However, since the total light output from a single halogen lamp is relatively small, as compared with conventional incandescent globes or fluorescent lighting, it is necessary in a jewelry showroom or store to use a relatively large number of halogen lamps.
A typical halogen lamp used in a showroom or store environment dissipates 50 watts of power, and operates from a 12 volt source normally provided from a transformer connected to the mains power supply. A typical jewelry store using 50 halogen spot lamps therefore dissipates 2,500 watts in lighting alone, plus the additional power consumption resulting from transformer inefficiency and losses in the relatively higher current 12 volt leads supplying the lamps. Since a significant proportion of this power is dissipated as heat, the overall heating effect of the lighting within the showroom may approximate that of a domestic bar radiator. This may in turn increase the demands on air conditioning within the store.
The relatively recent development of bright white-light LEDs (Light Emitting Diodes) has provided a possible alternative to halogen spot lamps. For example, white-light LEDs have been used to make small desktop displays that may be used to view articles of jewelry. In using such a display, a customer may hold an item of jewelry, or in the case of a ring, may wear the jewelry on their hand. The customer then places their hand within the desktop display box, the interior of which is illuminated with white-light LEDs. Since the LED light sources are very small, they can result in the production of significant fire and scintillation effects.
However, white-light LEDs may not provide a sufficiently natural source of light. Most bright white-light LEDs consist of a blue LED with a phosphor coating applied to the glass or plastic lens and cover that protect the LED and direct the light output. The blue light from the LED is absorbed by the phosphor coating, which then emits light across the visible spectrum to produce a substantially white light output. However, the light output generally retains a strong blue component that is not balanced by the other colours of the spectrum emitted by the phosphor coating. The result is a cold and blue dominated light output that tends to produce an unnatural and subjectively unpleasant rendering of many colours, and in particular of skin tones. The customer viewing their hand along with the article of jewelry under such lighting is likely to be aware that an unnatural light source is being used, and may therefore suspect that the lighting has been designed to artificially enhance the appearance of the jewelry within the store or showroom in ways that will not be reproduced in more normal or natural lighting environments.
It is therefore an object of the present invention to provide an alternative apparatus and method for display lighting which is especially suited for illuminating items of jewelry, for example within a store or showroom environment, and which mitigates the aforementioned problems of known showroom lighting systems.
Any discussion of documents, devices, acts or knowledge in this specification is included to explain the context of the invention. It should not be taken as an admission that any of the material formed part of the prior art base or the common general knowledge in the relevant art on or before the priority date of the following statements of invention, or of any claims appended hereto.